From: David Sterba Date: Tue, 1 Jul 2025 17:23:50 +0000 (+0200) Subject: btrfs: accessors: inline eb bounds check and factor out the error report X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d5a87dbd958398c1926dd35a328ccf89a410cbd2;p=thirdparty%2Flinux.git btrfs: accessors: inline eb bounds check and factor out the error report There's a check in each set/get helper if the requested range is within extent buffer bounds, and if it's not then report it. This was in an ASSERT statement so with CONFIG_BTRFS_ASSERT this crashes right away, on other configs this is only reported but reading out of the bounds is done anyway. There are currently no known reports of this particular condition failing. There are some drawbacks though. The behaviour dependence on the assertions being compiled in or not and a less visible effect of inlining report_setget_bounds() into each helper. As the bounds check is expected to succeed almost always it's ok to inline it but make the report a function and move it out of the helper completely (__cold puts it to a different section). This also skips reading/writing the requested range in case it fails. This improves stack usage significantly: btrfs_get_16 -48 (80 -> 32) btrfs_get_32 -48 (80 -> 32) btrfs_get_64 -48 (80 -> 32) btrfs_get_8 -48 (72 -> 24) btrfs_set_16 -56 (88 -> 32) btrfs_set_32 -56 (88 -> 32) btrfs_set_64 -56 (88 -> 32) btrfs_set_8 -48 (80 -> 32) NEW (48): report_setget_bounds 48 LOST/NEW DELTA: +48 PRE/POST DELTA: -360 Same as .ko size: text data bss dec hex filename 1456079 115665 16088 1587832 183a78 pre/btrfs.ko 1454951 115665 16088 1586704 183610 post/btrfs.ko DELTA: -1128 Reviewed-by: Boris Burkov Signed-off-by: David Sterba --- diff --git a/fs/btrfs/accessors.c b/fs/btrfs/accessors.c index 2e90b9b14e73f..a7b6b2d7bde22 100644 --- a/fs/btrfs/accessors.c +++ b/fs/btrfs/accessors.c @@ -9,20 +9,15 @@ #include "fs.h" #include "accessors.h" -static bool check_setget_bounds(const struct extent_buffer *eb, - const void *ptr, unsigned off, int size) +static void __cold report_setget_bounds(const struct extent_buffer *eb, + const void *ptr, unsigned off, int size) { - const unsigned long member_offset = (unsigned long)ptr + off; + unsigned long member_offset = (unsigned long)ptr + off; - if (unlikely(member_offset + size > eb->len)) { - btrfs_warn(eb->fs_info, - "bad eb member %s: ptr 0x%lx start %llu member offset %lu size %d", - (member_offset > eb->len ? "start" : "end"), - (unsigned long)ptr, eb->start, member_offset, size); - return false; - } - - return true; + btrfs_warn(eb->fs_info, + "bad eb member %s: ptr 0x%lx start %llu member offset %lu size %d", + (member_offset > eb->len ? "start" : "end"), + (unsigned long)ptr, eb->start, member_offset, size); } /* @@ -56,7 +51,10 @@ u##bits btrfs_get_##bits(const struct extent_buffer *eb, \ const int part = eb->folio_size - oil; \ u8 lebytes[sizeof(u##bits)]; \ \ - ASSERT(check_setget_bounds(eb, ptr, off, sizeof(u##bits))); \ + if (unlikely(member_offset + sizeof(u##bits) > eb->len)) { \ + report_setget_bounds(eb, ptr, off, sizeof(u##bits)); \ + return 0; \ + } \ if (INLINE_EXTENT_BUFFER_PAGES == 1 || likely(sizeof(u##bits) <= part)) \ return get_unaligned_le##bits(kaddr + oil); \ \ @@ -76,7 +74,10 @@ void btrfs_set_##bits(const struct extent_buffer *eb, void *ptr, \ const int part = eb->folio_size - oil; \ u8 lebytes[sizeof(u##bits)]; \ \ - ASSERT(check_setget_bounds(eb, ptr, off, sizeof(u##bits))); \ + if (unlikely(member_offset + sizeof(u##bits) > eb->len)) { \ + report_setget_bounds(eb, ptr, off, sizeof(u##bits)); \ + return; \ + } \ if (INLINE_EXTENT_BUFFER_PAGES == 1 || \ likely(sizeof(u##bits) <= part)) { \ put_unaligned_le##bits(val, kaddr + oil); \