| Message ID | 20181112160910.GA28440@redhat.com |
|---|---|
| State | In Next |
| Commit | 38691b047ef9d6e826ce4e442234226b853f7ffc |
| Headers | show |
| Series |
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| Related | show |
On Mon, Nov 12, 2018 at 10:09 AM, Oleg Nesterov <oleg@redhat.com> wrote: > get_arg_page() checks bprm->rlim_stack.rlim_cur and re-calculates the > "extra" size for argv/envp pointers every time, this is a bit ugly and > even not strictly correct: acct_arg_size() must not account this size. > > Remove all the rlimit code in get_arg_page(). Instead, add bprm->argmin > calculated once at the start of __do_execve_file() and change copy_strings > to check bprm->p >= bprm->argmin. > > The patch adds the new helper, prepare_arg_pages() which initializes > bprm->argc/envc and bprm->argmin. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Kees Cook <keescook@chromium.org> Thanks for nailing this all down. :) -Kees > --- > fs/exec.c | 103 +++++++++++++++++++++++------------------------- > include/linux/binfmts.h | 1 + > 2 files changed, 51 insertions(+), 53 deletions(-) > > diff --git a/fs/exec.c b/fs/exec.c > index fc281b7..61a5460 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -218,55 +218,10 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, > if (ret <= 0) > return NULL; > > - if (write) { > - unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; > - unsigned long ptr_size, limit; > - > - /* > - * Since the stack will hold pointers to the strings, we > - * must account for them as well. > - * > - * The size calculation is the entire vma while each arg page is > - * built, so each time we get here it's calculating how far it > - * is currently (rather than each call being just the newly > - * added size from the arg page). As a result, we need to > - * always add the entire size of the pointers, so that on the > - * last call to get_arg_page() we'll actually have the entire > - * correct size. > - */ > - ptr_size = (bprm->argc + bprm->envc) * sizeof(void *); > - if (ptr_size > ULONG_MAX - size) > - goto fail; > - size += ptr_size; > - > - acct_arg_size(bprm, size / PAGE_SIZE); > - > - /* > - * We've historically supported up to 32 pages (ARG_MAX) > - * of argument strings even with small stacks > - */ > - if (size <= ARG_MAX) > - return page; > - > - /* > - * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM > - * (whichever is smaller) for the argv+env strings. > - * This ensures that: > - * - the remaining binfmt code will not run out of stack space, > - * - the program will have a reasonable amount of stack left > - * to work from. > - */ > - limit = _STK_LIM / 4 * 3; > - limit = min(limit, bprm->rlim_stack.rlim_cur / 4); > - if (size > limit) > - goto fail; > - } > + if (write) > + acct_arg_size(bprm, vma_pages(bprm->vma)); > > return page; > - > -fail: > - put_page(page); > - return NULL; > } > > static void put_arg_page(struct page *page) > @@ -492,6 +447,50 @@ static int count(struct user_arg_ptr argv, int max) > return i; > } > > +static int prepare_arg_pages(struct linux_binprm *bprm, > + struct user_arg_ptr argv, struct user_arg_ptr envp) > +{ > + unsigned long limit, ptr_size; > + > + bprm->argc = count(argv, MAX_ARG_STRINGS); > + if (bprm->argc < 0) > + return bprm->argc; > + > + bprm->envc = count(envp, MAX_ARG_STRINGS); > + if (bprm->envc < 0) > + return bprm->envc; > + > + /* > + * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM > + * (whichever is smaller) for the argv+env strings. > + * This ensures that: > + * - the remaining binfmt code will not run out of stack space, > + * - the program will have a reasonable amount of stack left > + * to work from. > + */ > + limit = _STK_LIM / 4 * 3; > + limit = min(limit, bprm->rlim_stack.rlim_cur / 4); > + /* > + * We've historically supported up to 32 pages (ARG_MAX) > + * of argument strings even with small stacks > + */ > + limit = max(limit, (unsigned long)ARG_MAX); > + /* > + * We must account for the size of all the argv and envp pointers to > + * the argv and envp strings, since they will also take up space in > + * the stack. They aren't stored until much later when we can't > + * signal to the parent that the child has run out of stack space. > + * Instead, calculate it here so it's possible to fail gracefully. > + */ > + ptr_size = (bprm->argc + bprm->envc) * sizeof(void *); > + if (limit <= ptr_size) > + return -E2BIG; > + limit -= ptr_size; > + > + bprm->argmin = bprm->p - limit; > + return 0; > +} > + > /* > * 'copy_strings()' copies argument/environment strings from the old > * processes's memory to the new process's stack. The call to get_user_pages() > @@ -527,6 +526,8 @@ static int copy_strings(int argc, struct user_arg_ptr argv, > pos = bprm->p; > str += len; > bprm->p -= len; > + if (bprm->p < bprm->argmin) > + goto out; > > while (len > 0) { > int offset, bytes_to_copy; > @@ -1789,12 +1790,8 @@ static int __do_execve_file(int fd, struct filename *filename, > if (retval) > goto out_unmark; > > - bprm->argc = count(argv, MAX_ARG_STRINGS); > - if ((retval = bprm->argc) < 0) > - goto out; > - > - bprm->envc = count(envp, MAX_ARG_STRINGS); > - if ((retval = bprm->envc) < 0) > + retval = prepare_arg_pages(bprm, argv, envp); > + if (retval < 0) > goto out; > > retval = prepare_binprm(bprm); > diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h > index e9f5fe6..03200a8 100644 > --- a/include/linux/binfmts.h > +++ b/include/linux/binfmts.h > @@ -25,6 +25,7 @@ struct linux_binprm { > #endif > struct mm_struct *mm; > unsigned long p; /* current top of mem */ > + unsigned long argmin; /* rlimit marker for copy_strings() */ > unsigned int > /* > * True after the bprm_set_creds hook has been called once > -- > 2.5.0 > >
Hi, On Mon, Nov 12, 2018 at 05:09:10PM +0100, Oleg Nesterov wrote: > get_arg_page() checks bprm->rlim_stack.rlim_cur and re-calculates the > "extra" size for argv/envp pointers every time, this is a bit ugly and > even not strictly correct: acct_arg_size() must not account this size. > > Remove all the rlimit code in get_arg_page(). Instead, add bprm->argmin > calculated once at the start of __do_execve_file() and change copy_strings > to check bprm->p >= bprm->argmin. > > The patch adds the new helper, prepare_arg_pages() which initializes > bprm->argc/envc and bprm->argmin. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com> > Acked-by: Kees Cook <keescook@chromium.org> This patch results in various qemu boot failures in -next. Bisect logs are attached. It looks like all nommu boots are failing. I bisected an385 and m68k, but xtensa (kc705-nommu) fails with the same error. [ 5.416926] Run /sbin/init as init process [ 5.419792] Failed to execute /sbin/init (error -7) [ 5.421128] Run /sbin/init as init process [ 5.423284] Starting init: /sbin/init exists but couldn't execute it (error -7) [ 5.424747] Run /etc/init as init process [ 5.428507] Run /bin/init as init process [ 5.430478] Run /bin/sh as init process [ 5.433179] Starting init: /bin/sh exists but couldn't execute it (error -7) Guenter --- an385: # bad: [8c9733fd9806c71e7f2313a280f98cb3051f93df] Add linux-next specific files for 20181123 # good: [9ff01193a20d391e8dbce4403dd5ef87c7eaaca6] Linux 4.20-rc3 git bisect start 'HEAD' 'v4.20-rc3' # good: [34c2101b4f765edf1b91c2837da9c60fbf9f6912] Merge remote-tracking branch 'spi-nor/spi-nor/next' git bisect good 34c2101b4f765edf1b91c2837da9c60fbf9f6912 # good: [15367a0657fc8027ff3466bf0202bde9f270259b] Merge remote-tracking branch 'kgdb/kgdb-next' git bisect good 15367a0657fc8027ff3466bf0202bde9f270259b # good: [d29686ab179c34c5dbaac067a9effbeeb6a8073e] Merge remote-tracking branch 'soundwire/next' git bisect good d29686ab179c34c5dbaac067a9effbeeb6a8073e # good: [3381311f9a261c9d2863f0d52e9499c88ccb1f44] Merge remote-tracking branch 'cgroup/for-next' git bisect good 3381311f9a261c9d2863f0d52e9499c88ccb1f44 # good: [b5bf9c4c28a25b74475c3f3d3fe6d5d737629ab7] Merge remote-tracking branch 'pinctrl/for-next' git bisect good b5bf9c4c28a25b74475c3f3d3fe6d5d737629ab7 # good: [a75f6952444a401f5464e977caff2a84118b66c9] fs/epoll: deal with wait_queue only once git bisect good a75f6952444a401f5464e977caff2a84118b66c9 # good: [d83de16290eefb4372520a61744b11bddb6e8f7e] Merge remote-tracking branch 'slimbus/for-next' git bisect good d83de16290eefb4372520a61744b11bddb6e8f7e # good: [f2d2d58687c8300fe4ebf09d78b26cd68c825df7] Merge remote-tracking branch 'xarray/xarray' git bisect good f2d2d58687c8300fe4ebf09d78b26cd68c825df7 # bad: [eac22eb65c3cc96d8cb2c7aac7dd816030a86955] ipc: allow boot time extension of IPCMNI from 32k to 8M git bisect bad eac22eb65c3cc96d8cb2c7aac7dd816030a86955 # good: [fb95dde314b136e9598a56350b3de3994d272486] exec: increase BINPRM_BUF_SIZE to 256 git bisect good fb95dde314b136e9598a56350b3de3994d272486 # bad: [fb704fe633a3ca80a68282d5c3c665c4382f500b] exec-separate-mm_anonpages-and-rlimit_stack-accounting-checkpatch-fixes git bisect bad fb704fe633a3ca80a68282d5c3c665c4382f500b # bad: [eed684faf14610c2063c1f03e0a1f5ef56f23bb4] exec: separate MM_ANONPAGES and RLIMIT_STACK accounting git bisect bad eed684faf14610c2063c1f03e0a1f5ef56f23bb4 # first bad commit: [eed684faf14610c2063c1f03e0a1f5ef56f23bb4] exec: separate MM_ANONPAGES and RLIMIT_STACK accounting --- m68k: # bad: [8c9733fd9806c71e7f2313a280f98cb3051f93df] Add linux-next specific files for 20181123 # good: [9ff01193a20d391e8dbce4403dd5ef87c7eaaca6] Linux 4.20-rc3 git bisect start 'HEAD' 'v4.20-rc3' # good: [34c2101b4f765edf1b91c2837da9c60fbf9f6912] Merge remote-tracking branch 'spi-nor/spi-nor/next' git bisect good 34c2101b4f765edf1b91c2837da9c60fbf9f6912 # good: [15367a0657fc8027ff3466bf0202bde9f270259b] Merge remote-tracking branch 'kgdb/kgdb-next' git bisect good 15367a0657fc8027ff3466bf0202bde9f270259b # good: [d29686ab179c34c5dbaac067a9effbeeb6a8073e] Merge remote-tracking branch 'soundwire/next' git bisect good d29686ab179c34c5dbaac067a9effbeeb6a8073e # good: [3381311f9a261c9d2863f0d52e9499c88ccb1f44] Merge remote-tracking branch 'cgroup/for-next' git bisect good 3381311f9a261c9d2863f0d52e9499c88ccb1f44 # good: [b5bf9c4c28a25b74475c3f3d3fe6d5d737629ab7] Merge remote-tracking branch 'pinctrl/for-next' git bisect good b5bf9c4c28a25b74475c3f3d3fe6d5d737629ab7 # good: [a75f6952444a401f5464e977caff2a84118b66c9] fs/epoll: deal with wait_queue only once git bisect good a75f6952444a401f5464e977caff2a84118b66c9 # good: [d83de16290eefb4372520a61744b11bddb6e8f7e] Merge remote-tracking branch 'slimbus/for-next' git bisect good d83de16290eefb4372520a61744b11bddb6e8f7e # good: [f2d2d58687c8300fe4ebf09d78b26cd68c825df7] Merge remote-tracking branch 'xarray/xarray' git bisect good f2d2d58687c8300fe4ebf09d78b26cd68c825df7 # bad: [eac22eb65c3cc96d8cb2c7aac7dd816030a86955] ipc: allow boot time extension of IPCMNI from 32k to 8M git bisect bad eac22eb65c3cc96d8cb2c7aac7dd816030a86955 # good: [fb95dde314b136e9598a56350b3de3994d272486] exec: increase BINPRM_BUF_SIZE to 256 git bisect good fb95dde314b136e9598a56350b3de3994d272486 # bad: [fb704fe633a3ca80a68282d5c3c665c4382f500b] exec-separate-mm_anonpages-and-rlimit_stack-accounting-checkpatch-fixes git bisect bad fb704fe633a3ca80a68282d5c3c665c4382f500b # bad: [eed684faf14610c2063c1f03e0a1f5ef56f23bb4] exec: separate MM_ANONPAGES and RLIMIT_STACK accounting git bisect bad eed684faf14610c2063c1f03e0a1f5ef56f23bb4 # first bad commit: [eed684faf14610c2063c1f03e0a1f5ef56f23bb4] exec: separate MM_ANONPAGES and RLIMIT_STACK accounting
Hi Guenter, On 11/23, Guenter Roeck wrote: > > On Mon, Nov 12, 2018 at 05:09:10PM +0100, Oleg Nesterov wrote: > > get_arg_page() checks bprm->rlim_stack.rlim_cur and re-calculates the > > "extra" size for argv/envp pointers every time, this is a bit ugly and > > even not strictly correct: acct_arg_size() must not account this size. > > > > Remove all the rlimit code in get_arg_page(). Instead, add bprm->argmin > > calculated once at the start of __do_execve_file() and change copy_strings > > to check bprm->p >= bprm->argmin. > > > > The patch adds the new helper, prepare_arg_pages() which initializes > > bprm->argc/envc and bprm->argmin. > > > > Signed-off-by: Oleg Nesterov <oleg@redhat.com> > > Acked-by: Kees Cook <keescook@chromium.org> > > This patch results in various qemu boot failures in -next. Bisect logs > are attached. It looks like all nommu boots are failing. ^^^^^ Ah, thanks. Yes, I forgot about the !CONFIG_MMU version of get_arg_page() which doesn't check RLIMIT_STACK at all. I'll send the trivial fix. Meanwile, could you test the patch below? to ensure this is the only problem. Oleg. --- a/fs/exec.c +++ b/fs/exec.c @@ -526,8 +526,10 @@ static int copy_strings(int argc, struct user_arg_ptr argv, pos = bprm->p; str += len; bprm->p -= len; +#ifdef CONFIG_MMU if (bprm->p < bprm->argmin) goto out; +#endif while (len > 0) { int offset, bytes_to_copy;
Hi Oleg, On Mon, Nov 26, 2018 at 01:23:07PM +0100, Oleg Nesterov wrote: > Hi Guenter, > > On 11/23, Guenter Roeck wrote: > > > > On Mon, Nov 12, 2018 at 05:09:10PM +0100, Oleg Nesterov wrote: > > > get_arg_page() checks bprm->rlim_stack.rlim_cur and re-calculates the > > > "extra" size for argv/envp pointers every time, this is a bit ugly and > > > even not strictly correct: acct_arg_size() must not account this size. > > > > > > Remove all the rlimit code in get_arg_page(). Instead, add bprm->argmin > > > calculated once at the start of __do_execve_file() and change copy_strings > > > to check bprm->p >= bprm->argmin. > > > > > > The patch adds the new helper, prepare_arg_pages() which initializes > > > bprm->argc/envc and bprm->argmin. > > > > > > Signed-off-by: Oleg Nesterov <oleg@redhat.com> > > > Acked-by: Kees Cook <keescook@chromium.org> > > > > This patch results in various qemu boot failures in -next. Bisect logs > > are attached. It looks like all nommu boots are failing. > ^^^^^ > > Ah, thanks. > > Yes, I forgot about the !CONFIG_MMU version of get_arg_page() which doesn't > check RLIMIT_STACK at all. > > I'll send the trivial fix. Meanwile, could you test the patch below? to ensure > this is the only problem. > Tested-by: Guenter Roeck <linux@roeck-us.net> with arm:mps2-an385, xtensa:kc705-nommu, and m68k:mcf5208evb. Thanks, Guenter > Oleg. > > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -526,8 +526,10 @@ static int copy_strings(int argc, struct user_arg_ptr argv, > pos = bprm->p; > str += len; > bprm->p -= len; > +#ifdef CONFIG_MMU > if (bprm->p < bprm->argmin) > goto out; > +#endif > > while (len > 0) { > int offset, bytes_to_copy; >
diff --git a/fs/exec.c b/fs/exec.c index fc281b7..61a5460 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -218,55 +218,10 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, if (ret <= 0) return NULL; - if (write) { - unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; - unsigned long ptr_size, limit; - - /* - * Since the stack will hold pointers to the strings, we - * must account for them as well. - * - * The size calculation is the entire vma while each arg page is - * built, so each time we get here it's calculating how far it - * is currently (rather than each call being just the newly - * added size from the arg page). As a result, we need to - * always add the entire size of the pointers, so that on the - * last call to get_arg_page() we'll actually have the entire - * correct size. - */ - ptr_size = (bprm->argc + bprm->envc) * sizeof(void *); - if (ptr_size > ULONG_MAX - size) - goto fail; - size += ptr_size; - - acct_arg_size(bprm, size / PAGE_SIZE); - - /* - * We've historically supported up to 32 pages (ARG_MAX) - * of argument strings even with small stacks - */ - if (size <= ARG_MAX) - return page; - - /* - * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM - * (whichever is smaller) for the argv+env strings. - * This ensures that: - * - the remaining binfmt code will not run out of stack space, - * - the program will have a reasonable amount of stack left - * to work from. - */ - limit = _STK_LIM / 4 * 3; - limit = min(limit, bprm->rlim_stack.rlim_cur / 4); - if (size > limit) - goto fail; - } + if (write) + acct_arg_size(bprm, vma_pages(bprm->vma)); return page; - -fail: - put_page(page); - return NULL; } static void put_arg_page(struct page *page) @@ -492,6 +447,50 @@ static int count(struct user_arg_ptr argv, int max) return i; } +static int prepare_arg_pages(struct linux_binprm *bprm, + struct user_arg_ptr argv, struct user_arg_ptr envp) +{ + unsigned long limit, ptr_size; + + bprm->argc = count(argv, MAX_ARG_STRINGS); + if (bprm->argc < 0) + return bprm->argc; + + bprm->envc = count(envp, MAX_ARG_STRINGS); + if (bprm->envc < 0) + return bprm->envc; + + /* + * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM + * (whichever is smaller) for the argv+env strings. + * This ensures that: + * - the remaining binfmt code will not run out of stack space, + * - the program will have a reasonable amount of stack left + * to work from. + */ + limit = _STK_LIM / 4 * 3; + limit = min(limit, bprm->rlim_stack.rlim_cur / 4); + /* + * We've historically supported up to 32 pages (ARG_MAX) + * of argument strings even with small stacks + */ + limit = max(limit, (unsigned long)ARG_MAX); + /* + * We must account for the size of all the argv and envp pointers to + * the argv and envp strings, since they will also take up space in + * the stack. They aren't stored until much later when we can't + * signal to the parent that the child has run out of stack space. + * Instead, calculate it here so it's possible to fail gracefully. + */ + ptr_size = (bprm->argc + bprm->envc) * sizeof(void *); + if (limit <= ptr_size) + return -E2BIG; + limit -= ptr_size; + + bprm->argmin = bprm->p - limit; + return 0; +} + /* * 'copy_strings()' copies argument/environment strings from the old * processes's memory to the new process's stack. The call to get_user_pages() @@ -527,6 +526,8 @@ static int copy_strings(int argc, struct user_arg_ptr argv, pos = bprm->p; str += len; bprm->p -= len; + if (bprm->p < bprm->argmin) + goto out; while (len > 0) { int offset, bytes_to_copy; @@ -1789,12 +1790,8 @@ static int __do_execve_file(int fd, struct filename *filename, if (retval) goto out_unmark; - bprm->argc = count(argv, MAX_ARG_STRINGS); - if ((retval = bprm->argc) < 0) - goto out; - - bprm->envc = count(envp, MAX_ARG_STRINGS); - if ((retval = bprm->envc) < 0) + retval = prepare_arg_pages(bprm, argv, envp); + if (retval < 0) goto out; retval = prepare_binprm(bprm); diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index e9f5fe6..03200a8 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -25,6 +25,7 @@ struct linux_binprm { #endif struct mm_struct *mm; unsigned long p; /* current top of mem */ + unsigned long argmin; /* rlimit marker for copy_strings() */ unsigned int /* * True after the bprm_set_creds hook has been called once
get_arg_page() checks bprm->rlim_stack.rlim_cur and re-calculates the "extra" size for argv/envp pointers every time, this is a bit ugly and even not strictly correct: acct_arg_size() must not account this size. Remove all the rlimit code in get_arg_page(). Instead, add bprm->argmin calculated once at the start of __do_execve_file() and change copy_strings to check bprm->p >= bprm->argmin. The patch adds the new helper, prepare_arg_pages() which initializes bprm->argc/envc and bprm->argmin. Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- fs/exec.c | 103 +++++++++++++++++++++++------------------------- include/linux/binfmts.h | 1 + 2 files changed, 51 insertions(+), 53 deletions(-)