5.15-stable review patch. If anyone has any objections, please let me know.
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From: Kees Cook kees@kernel.org
[ Upstream commit 3eb3cd5992f7a0c37edc8d05b4c38c98758d8671 ]
Commit 04d82a6d0881 ("binfmt_flat: allow not offsetting data start") introduced a RISC-V specific variant of the FLAT format which does not allocate any space for the (obsolete) array of shared library pointers. However, it did not disable the code which initializes the array, resulting in the corruption of sizeof(long) bytes before the DATA segment, generally the end of the TEXT segment.
Introduce MAX_SHARED_LIBS_UPDATE which depends on the state of CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET to guard the initialization of the shared library pointer region so that it will only be initialized if space is reserved for it.
Fixes: 04d82a6d0881 ("binfmt_flat: allow not offsetting data start") Co-developed-by: Stefan O'Rear sorear@fastmail.com Signed-off-by: Stefan O'Rear sorear@fastmail.com Reviewed-by: Damien Le Moal dlemoal@kernel.org Acked-by: Greg Ungerer gerg@linux-m68k.org Link: https://lore.kernel.org/r/20240807195119.it.782-kees@kernel.org Signed-off-by: Kees Cook kees@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/binfmt_flat.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c index 7ca3e0db06ffa..250651cdce0a6 100644 --- a/fs/binfmt_flat.c +++ b/fs/binfmt_flat.c @@ -76,8 +76,10 @@
#ifdef CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET #define DATA_START_OFFSET_WORDS (0) +#define MAX_SHARED_LIBS_UPDATE (0) #else #define DATA_START_OFFSET_WORDS (MAX_SHARED_LIBS) +#define MAX_SHARED_LIBS_UPDATE (MAX_SHARED_LIBS) #endif
struct lib_info { @@ -991,7 +993,7 @@ static int load_flat_binary(struct linux_binprm *bprm) return res;
/* Update data segment pointers for all libraries */ - for (i = 0; i < MAX_SHARED_LIBS; i++) { + for (i = 0; i < MAX_SHARED_LIBS_UPDATE; i++) { if (!libinfo.lib_list[i].loaded) continue; for (j = 0; j < MAX_SHARED_LIBS; j++) {