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Code

perf symbol-minimal: Fix ehdr reading in filename__read_build_id

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The e_ident is part of the ehdr and so reading it a second time would
mean the read ehdr was displaced by 16-bytes. Switch from stdio to
open/read/lseek syscalls for similarity with the symbol-elf version of
the function and so that later changes can alter then open flags.

Fixes: fef8f648bb ("perf symbol: Fix use-after-free in filename__read_build_id")
Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250823000024.724394-2-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Ian Rogers 2025-08-22 17:00:23 -07:00 committed by Namhyung Kim
parent f79a62f4b3
commit ba0b7081f7
1 changed files with 27 additions and 28 deletions
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55
tools/perf/util/symbol-minimal.c
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@ -4,7 +4,6 @@
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
@ -88,11 +87,8 @@ int filename__read_debuglink(const char *filename __maybe_unused,
*/
int filename__read_build_id(const char *filename, struct build_id *bid)
{
FILE *fp;
int ret = -1;
int fd, ret = -1;
bool need_swap = false, elf32;
u8 e_ident[EI_NIDENT];
int i;
union {
struct {
Elf32_Ehdr ehdr32;
@ -103,28 +99,27 @@ int filename__read_build_id(const char *filename, struct build_id *bid)
Elf64_Phdr *phdr64;
};
} hdrs;
void *phdr;
size_t phdr_size;
void *buf = NULL;
size_t buf_size = 0;
void *phdr, *buf = NULL;
ssize_t phdr_size, ehdr_size, buf_size = 0;
fp = fopen(filename, "r");
if (fp == NULL)
fd = open(filename, O_RDONLY);
if (fd < 0)
return -1;
if (fread(e_ident, sizeof(e_ident), 1, fp) != 1)
if (read(fd, hdrs.ehdr32.e_ident, EI_NIDENT) != EI_NIDENT)
goto out;
if (memcmp(e_ident, ELFMAG, SELFMAG) ||
e_ident[EI_VERSION] != EV_CURRENT)
if (memcmp(hdrs.ehdr32.e_ident, ELFMAG, SELFMAG) ||
hdrs.ehdr32.e_ident[EI_VERSION] != EV_CURRENT)
goto out;
need_swap = check_need_swap(e_ident[EI_DATA]);
elf32 = e_ident[EI_CLASS] == ELFCLASS32;
need_swap = check_need_swap(hdrs.ehdr32.e_ident[EI_DATA]);
elf32 = hdrs.ehdr32.e_ident[EI_CLASS] == ELFCLASS32;
ehdr_size = (elf32 ? sizeof(hdrs.ehdr32) : sizeof(hdrs.ehdr64)) - EI_NIDENT;
if (fread(elf32 ? (void *)&hdrs.ehdr32 : (void *)&hdrs.ehdr64,
elf32 ? sizeof(hdrs.ehdr32) : sizeof(hdrs.ehdr64),
1, fp) != 1)
if (read(fd,
(elf32 ? (void *)&hdrs.ehdr32 : (void *)&hdrs.ehdr64) + EI_NIDENT,
ehdr_size) != ehdr_size)
goto out;
if (need_swap) {
@ -138,14 +133,18 @@ int filename__read_build_id(const char *filename, struct build_id *bid)
hdrs.ehdr64.e_phnum = bswap_16(hdrs.ehdr64.e_phnum);
}
}
phdr_size = elf32 ? hdrs.ehdr32.e_phentsize * hdrs.ehdr32.e_phnum
: hdrs.ehdr64.e_phentsize * hdrs.ehdr64.e_phnum;
if ((elf32 && hdrs.ehdr32.e_phentsize != sizeof(Elf32_Phdr)) ||
(!elf32 && hdrs.ehdr64.e_phentsize != sizeof(Elf64_Phdr)))
goto out;
phdr_size = elf32 ? sizeof(Elf32_Phdr) * hdrs.ehdr32.e_phnum
: sizeof(Elf64_Phdr) * hdrs.ehdr64.e_phnum;
phdr = malloc(phdr_size);
if (phdr == NULL)
goto out;
fseek(fp, elf32 ? hdrs.ehdr32.e_phoff : hdrs.ehdr64.e_phoff, SEEK_SET);
if (fread(phdr, phdr_size, 1, fp) != 1)
lseek(fd, elf32 ? hdrs.ehdr32.e_phoff : hdrs.ehdr64.e_phoff, SEEK_SET);
if (read(fd, phdr, phdr_size) != phdr_size)
goto out_free;
if (elf32)
@ -153,8 +152,8 @@ int filename__read_build_id(const char *filename, struct build_id *bid)
else
hdrs.phdr64 = phdr;
for (i = 0; i < elf32 ? hdrs.ehdr32.e_phnum : hdrs.ehdr64.e_phnum; i++) {
size_t p_filesz;
for (int i = 0; i < (elf32 ? hdrs.ehdr32.e_phnum : hdrs.ehdr64.e_phnum); i++) {
ssize_t p_filesz;
if (need_swap) {
if (elf32) {
@ -180,8 +179,8 @@ int filename__read_build_id(const char *filename, struct build_id *bid)
goto out_free;
buf = tmp;
}
fseek(fp, elf32 ? hdrs.phdr32[i].p_offset : hdrs.phdr64[i].p_offset, SEEK_SET);
if (fread(buf, p_filesz, 1, fp) != 1)
lseek(fd, elf32 ? hdrs.phdr32[i].p_offset : hdrs.phdr64[i].p_offset, SEEK_SET);
if (read(fd, buf, p_filesz) != p_filesz)
goto out_free;
ret = read_build_id(buf, p_filesz, bid, need_swap);
@ -194,7 +193,7 @@ out_free:
free(buf);
free(phdr);
out:
fclose(fp);
close(fd);
return ret;
}