diff mbox series

[v3,bpf-next,04/10] lib/buildid: remove single-page limit for PHDR search

Message ID 20240730203914.1182569-5-andrii@kernel.org (mailing list archive)
State New
Headers show
Series Harden and extend ELF build ID parsing logic | expand

Commit Message

Andrii Nakryiko July 30, 2024, 8:39 p.m. UTC 
Now that freader allows to access multiple pages transparently, there is
no need to limit program headers to the very first ELF file page. Remove
this limitation, but still put some sane limit on amount of program
headers that we are willing to iterate over (set arbitrarily to 256).

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 lib/buildid.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/lib/buildid.c b/lib/buildid.c
index ba453a3784d1..095e79158b85 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -8,6 +8,8 @@ 
 
 #define BUILD_ID 3
 
+#define MAX_PHDR_CNT 256
+
 struct freader {
 	void *buf;
 	u32 buf_sz;
@@ -217,9 +219,9 @@  static int get_build_id_32(struct freader *r, unsigned char *build_id, __u32 *si
 	phnum = READ_ONCE(ehdr->e_phnum);
 	phoff = READ_ONCE(ehdr->e_phoff);
 
-	/* only supports phdr that fits in one page */
-	if (phnum > (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
-		return -EINVAL;
+	/* set upper bound on amount of segments (phdrs) we iterate */
+	if (phnum > MAX_PHDR_CNT)
+		phnum = MAX_PHDR_CNT;
 
 	for (i = 0; i < phnum; ++i) {
 		phdr = freader_fetch(r, phoff + i * sizeof(Elf32_Phdr), sizeof(Elf32_Phdr));
@@ -250,9 +252,9 @@  static int get_build_id_64(struct freader *r, unsigned char *build_id, __u32 *si
 	phnum = READ_ONCE(ehdr->e_phnum);
 	phoff = READ_ONCE(ehdr->e_phoff);
 
-	/* only supports phdr that fits in one page */
-	if (phnum > (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
-		return -EINVAL;
+	/* set upper bound on amount of segments (phdrs) we iterate */
+	if (phnum > MAX_PHDR_CNT)
+		phnum = MAX_PHDR_CNT;
 
 	for (i = 0; i < phnum; ++i) {
 		phdr = freader_fetch(r, phoff + i * sizeof(Elf64_Phdr), sizeof(Elf64_Phdr));