kernel/git/stable/linux.git/fs/proc/base.c, branch linux-4.18.y

proc: restrict kernel stack dumps to root

2018-10-10T06:56:08+00:00

commit f8a00cef17206ecd1b30d3d9f99e10d9fa707aa7 upstream. Currently, you can use /proc/self/task/*/stack to cause a stack walk on a task you control while it is running on another CPU. That means that the stack can change under the stack walker. The stack walker does have guards against going completely off the rails and into random kernel memory, but it can interpret random data from your kernel stack as instruction pointers and stack pointers. This can cause exposure of kernel stack contents to userspace. Restrict the ability to inspect kernel stacks of arbitrary tasks to root in order to prevent a local attacker from exploiting racy stack unwinding to leak kernel task stack contents. See the added comment for a longer rationale. There don't seem to be any users of this userspace API that can't gracefully bail out if reading from the file fails. Therefore, I believe that this change is unlikely to break things. In the case that this patch does end up needing a revert, the next-best solution might be to fake a single-entry stack based on wchan. Link: http://lkml.kernel.org/r/20180927153316.200286-1-jannh@google.com Fixes: 2ec220e27f50 ("proc: add /proc/*/stack") Signed-off-by: Jann Horn Acked-by: Kees Cook Cc: Alexey Dobriyan Cc: Ken Chen Cc: Will Deacon Cc: Laura Abbott Cc: Andy Lutomirski Cc: Catalin Marinas Cc: Josh Poimboeuf Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H . Peter Anvin" Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

proc: fix missing final NUL in get_mm_cmdline() rewrite

2018-06-20T06:38:28+00:00

The rewrite of the cmdline fetching missed the fact that we used to also return the final terminating NUL character of the last argument. I hadn't noticed, and none of the tools I tested cared, but something obviously must care, because Michal Kubecek noticed the change in behavior. Tweak the "find the end" logic to actually include the NUL character, and once past the eend of argv, always start the strnlen() at the expected (original) argument end. This whole "allow people to rewrite their arguments in place" is a nasty hack and requires that odd slop handling at the end of the argv array, but it's our traditional model, so we continue to support it. Repored-and-bisected-by: Michal Kubecek Reviewed-and-tested-by: Michal Kubecek Cc: Alexey Dobriyan Signed-off-by: Linus Torvalds

proc: skip branch in /proc// lookup

2018-06-14T22:55:24+00:00

Code is structured like this: for ( ... p < last; p++) { if (memcmp == 0) break; } if (p >= last) ERROR OK gcc doesn't see that if if lookup succeeds than post loop branch will never be taken and skip it. [akpm@linux-foundation.org: proc_pident_instantiate() no longer takes an inode*] Link: http://lkml.kernel.org/r/20180423213954.GD9043@avx2 Signed-off-by: Alexey Dobriyan Reviewed-by: Andrew Morton Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

treewide: kmalloc() -> kmalloc_array()

2018-06-12T23:19:22+00:00

The kmalloc() function has a 2-factor argument form, kmalloc_array(). This patch replaces cases of: kmalloc(a * b, gfp) with: kmalloc_array(a * b, gfp) as well as handling cases of: kmalloc(a * b * c, gfp) with: kmalloc(array3_size(a, b, c), gfp) as it's slightly less ugly than: kmalloc_array(array_size(a, b), c, gfp) This does, however, attempt to ignore constant size factors like: kmalloc(4 * 1024, gfp) though any constants defined via macros get caught up in the conversion. Any factors with a sizeof() of "unsigned char", "char", and "u8" were dropped, since they're redundant. The tools/ directory was manually excluded, since it has its own implementation of kmalloc(). The Coccinelle script used for this was: // Fix redundant parens around sizeof(). @@ type TYPE; expression THING, E; @@ ( kmalloc( - (sizeof(TYPE)) * E + sizeof(TYPE) * E , ...) | kmalloc( - (sizeof(THING)) * E + sizeof(THING) * E , ...) ) // Drop single-byte sizes and redundant parens. @@ expression COUNT; typedef u8; typedef __u8; @@ ( kmalloc( - sizeof(u8) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(__u8) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(char) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(unsigned char) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(u8) * COUNT + COUNT , ...) | kmalloc( - sizeof(__u8) * COUNT + COUNT , ...) | kmalloc( - sizeof(char) * COUNT + COUNT , ...) | kmalloc( - sizeof(unsigned char) * COUNT + COUNT , ...) ) // 2-factor product with sizeof(type/expression) and identifier or constant. @@ type TYPE; expression THING; identifier COUNT_ID; constant COUNT_CONST; @@ ( - kmalloc + kmalloc_array ( - sizeof(TYPE) * (COUNT_ID) + COUNT_ID, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * COUNT_ID + COUNT_ID, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * (COUNT_CONST) + COUNT_CONST, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * COUNT_CONST + COUNT_CONST, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * (COUNT_ID) + COUNT_ID, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * COUNT_ID + COUNT_ID, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * (COUNT_CONST) + COUNT_CONST, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * COUNT_CONST + COUNT_CONST, sizeof(THING) , ...) ) // 2-factor product, only identifiers. @@ identifier SIZE, COUNT; @@ - kmalloc + kmalloc_array ( - SIZE * COUNT + COUNT, SIZE , ...) // 3-factor product with 1 sizeof(type) or sizeof(expression), with // redundant parens removed. @@ expression THING; identifier STRIDE, COUNT; type TYPE; @@ ( kmalloc( - sizeof(TYPE) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(TYPE) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(TYPE) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(TYPE) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(THING) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kmalloc( - sizeof(THING) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kmalloc( - sizeof(THING) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kmalloc( - sizeof(THING) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) ) // 3-factor product with 2 sizeof(variable), with redundant parens removed. @@ expression THING1, THING2; identifier COUNT; type TYPE1, TYPE2; @@ ( kmalloc( - sizeof(TYPE1) * sizeof(TYPE2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | kmalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | kmalloc( - sizeof(THING1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | kmalloc( - sizeof(THING1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | kmalloc( - sizeof(TYPE1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) | kmalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) ) // 3-factor product, only identifiers, with redundant parens removed. @@ identifier STRIDE, SIZE, COUNT; @@ ( kmalloc( - (COUNT) * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - (COUNT) * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - (COUNT) * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - (COUNT) * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) ) // Any remaining multi-factor products, first at least 3-factor products, // when they're not all constants... @@ expression E1, E2, E3; constant C1, C2, C3; @@ ( kmalloc(C1 * C2 * C3, ...) | kmalloc( - (E1) * E2 * E3 + array3_size(E1, E2, E3) , ...) | kmalloc( - (E1) * (E2) * E3 + array3_size(E1, E2, E3) , ...) | kmalloc( - (E1) * (E2) * (E3) + array3_size(E1, E2, E3) , ...) | kmalloc( - E1 * E2 * E3 + array3_size(E1, E2, E3) , ...) ) // And then all remaining 2 factors products when they're not all constants, // keeping sizeof() as the second factor argument. @@ expression THING, E1, E2; type TYPE; constant C1, C2, C3; @@ ( kmalloc(sizeof(THING) * C2, ...) | kmalloc(sizeof(TYPE) * C2, ...) | kmalloc(C1 * C2 * C3, ...) | kmalloc(C1 * C2, ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * (E2) + E2, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * E2 + E2, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * (E2) + E2, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * E2 + E2, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - (E1) * E2 + E1, E2 , ...) | - kmalloc + kmalloc_array ( - (E1) * (E2) + E1, E2 , ...) | - kmalloc + kmalloc_array ( - E1 * E2 + E1, E2 , ...) ) Signed-off-by: Kees Cook

Merge branch 'proc-cmdline'

2018-06-09T22:31:35+00:00

Merge proc_cmdline simplifications. This re-writes the get_mm_cmdline() logic to be rather simpler than it used to be, and makes the semantics for "cmdline goes past the end of the original area" more natural. You _can_ use prctl(PR_SET_MM) to just point your command line somewhere else entirely, but the traditional model is to just edit things in place and that still needs to continue to work. At least this way the code makes some sense. * proc-cmdline: fs/proc: simplify and clarify get_mm_cmdline() function fs/proc: re-factor proc_pid_cmdline_read() a bit

Merge branch 'work.lookup' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2018-06-08T16:56:38+00:00

Pull proc_fill_cache regression fix from Al Viro: "Regression fix for proc_fill_cache() braino introduced when switching instantiate() callback to d_splice_alias()" * 'work.lookup' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: fix proc_fill_cache() in case of d_alloc_parallel() failure

fix proc_fill_cache() in case of d_alloc_parallel() failure

2018-06-08T05:17:11+00:00

If d_alloc_parallel() returns ERR_PTR(...), we don't want to dput() that. Small reorganization allows to have all error-in-lookup cases rejoin the main codepath after dput(child), avoiding the entire problem. Spotted-by: Tetsuo Handa Fixes: 0168b9e38c42 "procfs: switch instantiate_t to d_splice_alias()" Signed-off-by: Al Viro

proc: use "unsigned int" for /proc/*/stack

2018-06-08T00:34:38+00:00

struct stack_trace::nr_entries is defined as "unsigned int" (YAY!) so the iterator should be unsigned as well. It saves 1 byte of code or something like that. Link: http://lkml.kernel.org/r/20180423215248.GG9043@avx2 Signed-off-by: Alexey Dobriyan Reviewed-by: Andrew Morton Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc: use "unsigned int" in proc_fill_cache()

2018-06-08T00:34:38+00:00

All those lengths are unsigned as they should be. Link: http://lkml.kernel.org/r/20180423213751.GC9043@avx2 Signed-off-by: Alexey Dobriyan Reviewed-by: Andrew Morton Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc: smaller RCU section in ->getattr()

2018-06-08T00:34:38+00:00

struct kstat is thread local. Link: http://lkml.kernel.org/r/20180423213626.GB9043@avx2 Signed-off-by: Alexey Dobriyan Reviewed-by: Andrew Morton Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/git/stable/linux.git/fs/proc/base.c, branch linux-4.18.y

proc: restrict kernel stack dumps to root

proc: fix missing final NUL in get_mm_cmdline() rewrite

proc: skip branch in /proc/*/* lookup

treewide: kmalloc() -> kmalloc_array()

Merge branch 'proc-cmdline'

Merge branch 'work.lookup' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

fix proc_fill_cache() in case of d_alloc_parallel() failure

proc: use "unsigned int" for /proc/*/stack

proc: use "unsigned int" in proc_fill_cache()

proc: smaller RCU section in ->getattr()

proc: skip branch in /proc// lookup